I'm using a similar cable on both my VIC & C16, I got mine from ebay seller Retrocomputershack, it's works lovely and is very well made. I also bought a SCART lead for my speccy +2 from them and that is up to the same high standards.

If you have a soldering iron and a nice steady hand you can build one yourself.Anyway, if it works for the C64 it will work for the VIC-20. The pinouts on the ports are almost identical.You may need to adjust your picture though.